Screw clamps are widely used in particular in household installation technology and are used for the purpose of connecting electrical connecting conductors to an installation device, by way of example a circuit breaker or a fault-current circuit breaker.
Such installation switching devices comprise a housing that is embodied from an insulating material and comprises at least one front wall, a fastening wall that lies opposite said front wall and it is possible to provide on said fastening wall fastening devices for snapping on or fastening in any other form the installation switching device to a mounting rail or to another fastening device, said housing that is embodied from an insulating material also comprises narrow and broad sides that are connected to the front wall and the fastening wall.
The screw clamps for connecting the connecting conductor are typically attached in the region of the narrow sides in the installation switching device. The further construction elements or assemblies that are required for the intended function of the installation switching device are located in the interior of the installation switching device, said construction elements or assembles being by way of example triggers, switching levers and contact pieces, an arc quenching device, adjusting devices etc.
Known screw clamps comprise a clamping frame that has a rectangular cross section and a clamping screw that protrudes into the clamping frame through a threaded hole in a first transverse arm of the clamping frame. The clamping frame is moved along the axis of the clamping screw by means of rotating the clamping screw. A clamping space for fixedly clamping a connecting conductor is formed in the interior of the clamping frame.
A connecting conductor that is inserted into the clamping frame is consequently fixedly clamped in the clamping space.
A contact clamp that is referred to as a so-called rising clamp, a screw clamp having a clamping frame that is approximately rectangular in shape, is disclosed in DE 198 05 909 A1. In the case of the contact clamp disclosed in DE 198 05 909 A1, when a connecting conductor is being clamped under the influence of the clamping screw, the rectangular clamping frame is displaced relative to a contact rail that is inserted into the interior of the clamping frame, as a result of which the connecting conductor is fixedly clamped in the space between the clamping frame and the face of the contact rail that is remote from the clamping screw.
DE 10 2007 060 077 A1 discloses an installation switching device having a similarly constructed screw clamp that is also embodied in the manner of a rising clamp, wherein the part of the clamping frame that when in the assembled position can be touched through the insertion opening from outside the device housing is covered by an insulating material in the form of an insulating part that is plate-shaped and is latched in the forwards direction to the clamping frame in the region of the lower transverse arm of the clamping frame. It is necessary to attach the insulating part to the clamping frame prior to assembling the connecting clamp in the device housing, and in the region in which the insulating part is attached said insulating part increases the dimensions of the clamping frame forwards in the direction of the insertion opening, said insulating part increases as the space required for the connecting clamp. When a clamp is not completely opened, a free space occurs between the lower transverse piece of the clamping frame and the lower edge of the conductor insertion opening and it is possible for a connecting conductor to be incorrectly inserted into said free space so that the connecting conductor would not be inserted into the interior of the connecting clamp but rather would be inserted adjacent to said clamp, and this is also referred to as an incorrect insertion procedure. An incorrect insertion procedure must be avoided during the installation procedure.